CSNI Workshop

Jeju Island, Korea, 6-8 November 2006

Hosted by the Korea Atomic Energy Research Institute (KAERI) and the Korea Institute Of Nuclear Safety (KINS) In co-operation with the International Atomic Energy Agency (IAEA)

The methodology of seismic probabilistic safety assessment (PSA) for nuclear installations was first developed in the late 1970s. Over the years it has evolved so that today it is judged to be a mature methodology for assessing the risk to nuclear installations from earthquakes. A related methodology, the seismic margin assessment (SMA) methodology developed in the mid-1980s, has also been widely used.

Seismic PSA results have enabled both plant managerial personnel and regulators to concentrate their efforts and resources where it matters most, and in the process to improve safety significantly - often at low cost. For example, seismic PSA / margin studies often identify anchorage problems with electrical equipment, pumps, large tanks, and relay chatter. These problems can usually be fixed without large expense.

The NEA sponsored a workshop on seismic risk in Tokyo in August 1999 to discuss seismic PSA and SMA methodologies for nuclear installations. It was organised by the CSNI Principal Working Group 5 that later became WGRISK. The workshop report [1] provides a valuable summary of the state of the art of seismic PSA at that time, and includes findings and recommendations to guide the future work of both researchers and analysts. The workshop itself had the benefit of a 1998 state of the art report that was commissioned by the CSNI [2]. Late, in 2002, the CSNI adopted a "Topical Opinion Paper on Seismic PSA" [3], based principally on the deliberations and conclusions from the Tokyo workshop.

In the intervening years since the Tokyo workshop, the methodology of seismic PSA has been applied widely around the world at many nuclear power plants. There have also been technical advances in several aspects of the overall methodology. A major new development is the publication, under the auspices of the American Nuclear Society, of a methodology standard for seismic PSA and SMA [4]. The time seems ripe for a specialist meeting to discuss these advances, develop new findings and recommendations and provide the community of seismic risk analysts with a forum for discussing the current status of the field. The meeting will also serve as a forum to discuss items related to two IAEA safety documents in preparation; "Seismic evaluation and upgrading of existing NPPs" and "Probabilistic seismic hazard analysis for NPP sites" [5]

Workshop objectives

The main objectives of the meeting are:

To provide a forum to review the recent advances in methodology and practical application of seismic PSA and seismic margin analysis (SMA) for nuclear installations;

To discuss various uses of seismic PSA and SMA, taking into account both the merits and the limitations of these methods;

To review the state of the art, so as to provide guidance for conducting seismic PSA and SMA studies;

To discuss and review the recent work to develop a methodology standard and guideline documents for seismic PSA and SMA [4];

To discuss methodological issues and to identify areas where further research is needed for enhancing the usefulness of seismic PSA;

To review the findings and recommendations of the 1999 Tokyo workshop in light of advances since that time;

To develop a new set of findings and recommendations to guide the future national and international work of both researchers and analysts to make further improvements in quality as wells as in uses of PSA and SMA, based on the deliberations of the meeting.

The emphasis of the specialist meeting is on exchanging ideas on effective ways of using seismic PSA and SMA, rather than on simply reporting the numerical results of studies on specific plants. However, discussion of specific results is always appropriate to the extent that general insights can be drawn from them.